10.6.1 Initially,
meshing gears are to be carefully matched on the basis of the accuracy
measurements taken. The alignment is to be demonstrated in the workshop
by meshing in the gearbox without oil clearance in the bearings. Meshing
is to be carried out with the gears locating in their light load positions
and a load sufficient to overcome pinion weight and axial movement
is to be imposed.
10.6.2 The
gears are to be suitably coated to demonstrate the contact marking.
The thickness of the coating to determine the contact marking is not
to exceed 0,005 mm. The marking is to reflect the accuracy grade specified
and end relief, crowning or helix correction, where these have been
applied.
10.6.3 For
gears without crowning or helix correction the marking is to be not
less than shown in Table 3.10.1 No load tooth contact
marking.
Table 3.10.1 No load tooth contact
marking
| ISO accuracy
grade
|
Contact marking
area
|
| Q ≤
5
|
50%
b x 40% h
w + 40% b x 20% h
w
|
| Q ≥ 6
|
35% b x 40%
h
w + 35% b x 20% h
w
|
Note
1. Where b is the face width and
h
w is the working tooth depth.
Note
2. For spur gears, the values of h
w should be increased by a further 10%
|
10.6.4 Where
allowance has been given for end relief, crowning or helix correction,
the normal shop meshing tests are to be supplemented by tooth alignment
traces or other approved means to demonstrate the effectiveness of
such modifications.
10.6.5 For
gears with crowning or helix correction the marking is to correspond,
to the designed no load contact pattern.
10.6.6 A
permanent record is to be made of the meshing contact for purpose
of checking the alignment when installed on board the craft.
10.6.7 The
full load tooth contact marking is to be not less than shown in Table 3.10.2 Full load tooth contact
marking
Table 3.10.2 Full load tooth contact
marking
| ISO accuracy
grade
|
Contact marking
area
|
| Q ≤
5
|
60%
b x 70% h
w + 30% b x 50% h
w
|
| Q ≥ 6
|
45% b x 60%
h
w + 35% b x 40% h
w
|
Note
1. Where b is the face width and
h
w is the working tooth depth.
Note
2. For spur gears, the values of h
w should be increased by a further 10%
|
10.6.8 Where,
due to the compactness of the gear unit, meshing tests of individual
units cannot be verified visually, consideration may be given to the
gear manufacturer providing suitable evidence that the design meshing
condition has been attained on units of the same design.
10.6.9 The
normal backlash between any pair of gears should not be less than:
+ 0,1 mm
where
|
αn
|
= |
normal
pressure angle, in degrees |
|
a
|
= |
centre
distance, in mm. |